AP BIOLOGY

Detailed explanation-1: -This phenomenon is called tropism. In positive phototropism, stems bend toward the light, and in negative phototropism, roots move away from the light source. In tropism, plants show their movement towards or away from the direction of a stimulus.

Detailed explanation-2: -A tropism is plant movement in response to an external stimulus in the environment. If a plant moves towards a stimulus, then it exhibits positive tropism; if a plant moves away from a stimulus, then it exhibits negative tropism.

Detailed explanation-3: -Sunlight acts as a stimulus for the growth of organisms towards the light (positive phototropism) or away from light (negative phototropism).

Detailed explanation-4: -While gravitropism is the predominant tropistic response in roots, phototropism also plays a role in the oriented growth in this organ in flowering plants. In blue or white light, roots exhibit negative phototropism, but red light induces positive phototropism.

Detailed explanation-5: -Positive phototropism is growth towards a light source; negative phototropism is growth away from light.